Evaluation of native Earth system model output with ESMValTool v2.6.0

[摘要] Earth system models (ESMs) are state-of-the-art climate models that allow numerical simulationsof the past, present-day, and future climate. To extend our understanding of the Earth systemand improve climate change projections, the complexity of ESMs heavily increased over the last decades.As a consequence, the amount and volume of data provided by ESMs has increased considerably.Innovative tools for a comprehensive model evaluation and analysis are required to assessthe performance of these increasingly complex ESMs against observations or reanalyses.One of these tools is the Earth System Model Evaluation Tool (ESMValTool), a community diagnosticand performance metrics tool for the evaluation of ESMs. Input data for ESMValTool needs to beformatted according to the CMOR (Climate Model Output Rewriter) standard, a process thatis usually referred to as “CMORization”. While this is a quasi-standard for large modelintercomparison projects like the Coupled Model Intercomparison Project (CMIP), this complicatesthe application of ESMValTool to non-CMOR-compliant climate model output. In this paper, we describe an extension of ESMValTool introduced in v2.6.0that allows seamless reading and processing of“native” climate model output, i.e., operational output produced by running the climatemodel through the standard workflow of the corresponding modeling institute. This isachieved by an extension of ESMValTool's preprocessing pipeline that performs a CMOR-like reformattingof the native model output during runtime. Thus, the rich collection of diagnostics provided byESMValTool is now fully available for these models. For models that use unstructured grids, afurther preprocessing step required to apply many common diagnostics is regridding to a regularlatitude–longitude grid. Extensions to ESMValTool's regridding functions described hereallow for more flexible interpolation schemes that can be used onunstructured grids. Currently, ESMValTool supports nearest-neighbor, bilinear, and first-orderconservative regridding from unstructured grids to regular grids. Example applications of this new native model support are the evaluation of new model setupsagainst predecessor versions, assessing of the performance of different simulations againstobservations, CMORization of native model data for contributions to model intercomparison projects,and monitoring of running climate model simulations. For the latter, new general-purposediagnostics have been added to ESMValTool that are able to plot a wide range of variable types.Currently, five climate models are supported: CESM2 (experimental; at the moment, only surfacevariables are available), EC-Earth3, EMAC, ICON, and IPSL-CM6. As the framework for the CMOR-likereformatting of native model output described here is implemented in a general way, support forother climate models can be easily added.

[学科分类] 土木及结构工程学